1. Field of the Invention:
The present invention relates to a method of code transmission, and more particularly, to such a method in which a code is agreed upon in advance between the transmitting and receiving stations, having corresponding ciphering machines for the transmission and reception of encoded messages.
2. The Prior Art:
It is generally known to provide cipher machines at transmitting and receiving stations, for the transmission and reception of encoded messages. At the transmitting station, messages from a terminal are encoded by means of a cipher machine and fed to a long distance line by a transmission unit. At the receiving station, messages are received and decoded, employing a corresponding cipher machine, and fed to a receiving terminal. The transmitting and receiving units may be interconnected either by a dedicated connection, or by a network such as a dial switching network or the like.
Such stations are able to carry on communication by means of clear transmission, that is, messages which are not coded with any special code, but encoded transmissions are preferred when secrecy is desired, in order to make it more difficult for third parties to become cognizant of the message. The code necessary for such a transmission can be agreed upon in advance, however, there is no normal means of insuring that the transmission is taking place with the desired station.